<li><a href="#Chapter11">ADVANCED AND EXPERIMENTAL FUNCTIONS</a></li>
<li><a href="#Chapter12">Candidate API for promotion into stable</a></li>
<li><a href="#Chapter13">Memory management</a></li>
-<li><a href="#Chapter14">Purely experimental API</a></li>
-<li><a href="#Chapter15">Frame size functions</a></li>
-<li><a href="#Chapter16">Memory management</a></li>
-<li><a href="#Chapter17">Advanced compression functions</a></li>
-<li><a href="#Chapter18">Advanced decompression functions</a></li>
-<li><a href="#Chapter19">Advanced streaming functions</a></li>
-<li><a href="#Chapter20">Buffer-less and synchronous inner streaming functions</a></li>
-<li><a href="#Chapter21">Buffer-less streaming compression (synchronous mode)</a></li>
-<li><a href="#Chapter22">Buffer-less streaming decompression (synchronous mode)</a></li>
-<li><a href="#Chapter23">New advanced API (experimental)</a></li>
+<li><a href="#Chapter14">Advanced compression API</a></li>
+<li><a href="#Chapter15">experimental API (static linking only)</a></li>
+<li><a href="#Chapter16">Frame size functions</a></li>
+<li><a href="#Chapter17">Memory management</a></li>
+<li><a href="#Chapter18">Advanced compression functions</a></li>
+<li><a href="#Chapter19">Advanced decompression functions</a></li>
+<li><a href="#Chapter20">Advanced streaming functions</a></li>
+<li><a href="#Chapter21">Buffer-less and synchronous inner streaming functions</a></li>
+<li><a href="#Chapter22">Buffer-less streaming compression (synchronous mode)</a></li>
+<li><a href="#Chapter23">Buffer-less streaming decompression (synchronous mode)</a></li>
<li><a href="#Chapter24">Block level API</a></li>
</ol>
<hr>
Object memory usage can evolve when re-used.
</p></pre><BR>
-<a name="Chapter14"></a><h2>Purely experimental API</h2><pre>
- The following symbols and constants
- are not planned to join "stable API" status anytime soon.
- Some will never reach "stable", and remain in the static_only section.
- Some of them might be removed in the future.
-
-<BR></pre>
-
-<pre><b>typedef enum { ZSTD_fast=1,
- ZSTD_dfast=2,
- ZSTD_greedy=3,
- ZSTD_lazy=4,
- ZSTD_lazy2=5,
- ZSTD_btlazy2=6,
- ZSTD_btopt=7,
- ZSTD_btultra=8
- </b>/* note : new strategies might be added in the future */<b>
- } ZSTD_strategy;
-</b></pre><BR>
-<pre><b>typedef struct {
- unsigned windowLog; </b>/**< largest match distance : larger == more compression, more memory needed during decompression */<b>
- unsigned chainLog; </b>/**< fully searched segment : larger == more compression, slower, more memory (useless for fast) */<b>
- unsigned hashLog; </b>/**< dispatch table : larger == faster, more memory */<b>
- unsigned searchLog; </b>/**< nb of searches : larger == more compression, slower */<b>
- unsigned searchLength; </b>/**< match length searched : larger == faster decompression, sometimes less compression */<b>
- unsigned targetLength; </b>/**< acceptable match size for optimal parser (only) : larger == more compression, slower */<b>
- ZSTD_strategy strategy; </b>/**< see ZSTD_strategy definition above */<b>
-} ZSTD_compressionParameters;
-</b></pre><BR>
-<pre><b>typedef struct {
- unsigned contentSizeFlag; </b>/**< 1: content size will be in frame header (when known) */<b>
- unsigned checksumFlag; </b>/**< 1: generate a 32-bits checksum using XXH64 algorithm at end of frame, for error detection */<b>
- unsigned noDictIDFlag; </b>/**< 1: no dictID will be saved into frame header (dictID is only useful for dictionary compression) */<b>
-} ZSTD_frameParameters;
-</b></pre><BR>
-<pre><b>typedef struct {
- ZSTD_compressionParameters cParams;
- ZSTD_frameParameters fParams;
-} ZSTD_parameters;
-</b></pre><BR>
-<pre><b>typedef enum {
- ZSTD_dct_auto = 0, </b>/* dictionary is "full" when starting with ZSTD_MAGIC_DICTIONARY, otherwise it is "rawContent" */<b>
- ZSTD_dct_rawContent = 1, </b>/* ensures dictionary is always loaded as rawContent, even if it starts with ZSTD_MAGIC_DICTIONARY */<b>
- ZSTD_dct_fullDict = 2 </b>/* refuses to load a dictionary if it does not respect Zstandard's specification, starting with ZSTD_MAGIC_DICTIONARY */<b>
-} ZSTD_dictContentType_e;
-</b></pre><BR>
-<pre><b>typedef enum {
- ZSTD_dlm_byCopy = 0, </b>/**< Copy dictionary content internally */<b>
- ZSTD_dlm_byRef = 1, </b>/**< Reference dictionary content -- the dictionary buffer must outlive its users. */<b>
-} ZSTD_dictLoadMethod_e;
-</b></pre><BR>
-<a name="Chapter15"></a><h2>Frame size functions</h2><pre></pre>
-
-<pre><b>size_t ZSTD_findFrameCompressedSize(const void* src, size_t srcSize);
-</b><p> `src` should point to the start of a ZSTD encoded frame or skippable frame
- `srcSize` must be >= first frame size
- @return : the compressed size of the first frame starting at `src`,
- suitable to pass to `ZSTD_decompress` or similar,
- or an error code if input is invalid
-</p></pre><BR>
-
-<pre><b>unsigned long long ZSTD_findDecompressedSize(const void* src, size_t srcSize);
-</b><p> `src` should point the start of a series of ZSTD encoded and/or skippable frames
- `srcSize` must be the _exact_ size of this series
- (i.e. there should be a frame boundary exactly at `srcSize` bytes after `src`)
- @return : - decompressed size of all data in all successive frames
- - if the decompressed size cannot be determined: ZSTD_CONTENTSIZE_UNKNOWN
- - if an error occurred: ZSTD_CONTENTSIZE_ERROR
-
- note 1 : decompressed size is an optional field, that may not be present, especially in streaming mode.
- When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size.
- In which case, it's necessary to use streaming mode to decompress data.
- note 2 : decompressed size is always present when compression is done with ZSTD_compress()
- note 3 : decompressed size can be very large (64-bits value),
- potentially larger than what local system can handle as a single memory segment.
- In which case, it's necessary to use streaming mode to decompress data.
- note 4 : If source is untrusted, decompressed size could be wrong or intentionally modified.
- Always ensure result fits within application's authorized limits.
- Each application can set its own limits.
- note 5 : ZSTD_findDecompressedSize handles multiple frames, and so it must traverse the input to
- read each contained frame header. This is fast as most of the data is skipped,
- however it does mean that all frame data must be present and valid.
-</p></pre><BR>
-
-<pre><b>size_t ZSTD_frameHeaderSize(const void* src, size_t srcSize);
-</b><p> srcSize must be >= ZSTD_frameHeaderSize_prefix.
- @return : size of the Frame Header,
- or an error code (if srcSize is too small)
-</p></pre><BR>
-
-<a name="Chapter16"></a><h2>Memory management</h2><pre></pre>
-
-<pre><b>size_t ZSTD_estimateCCtxSize(int compressionLevel);
-size_t ZSTD_estimateCCtxSize_usingCParams(ZSTD_compressionParameters cParams);
-size_t ZSTD_estimateCCtxSize_usingCCtxParams(const ZSTD_CCtx_params* params);
-size_t ZSTD_estimateDCtxSize(void);
-</b><p> These functions make it possible to estimate memory usage
- of a future {D,C}Ctx, before its creation.
- ZSTD_estimateCCtxSize() will provide a budget large enough for any compression level up to selected one.
- It will also consider src size to be arbitrarily "large", which is worst case.
- If srcSize is known to always be small, ZSTD_estimateCCtxSize_usingCParams() can provide a tighter estimation.
- ZSTD_estimateCCtxSize_usingCParams() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel.
- ZSTD_estimateCCtxSize_usingCCtxParams() can be used in tandem with ZSTD_CCtxParam_setParameter(). Only single-threaded compression is supported. This function will return an error code if ZSTD_p_nbWorkers is >= 1.
- Note : CCtx size estimation is only correct for single-threaded compression.
-</p></pre><BR>
-
-<pre><b>size_t ZSTD_estimateCStreamSize(int compressionLevel);
-size_t ZSTD_estimateCStreamSize_usingCParams(ZSTD_compressionParameters cParams);
-size_t ZSTD_estimateCStreamSize_usingCCtxParams(const ZSTD_CCtx_params* params);
-size_t ZSTD_estimateDStreamSize(size_t windowSize);
-size_t ZSTD_estimateDStreamSize_fromFrame(const void* src, size_t srcSize);
-</b><p> ZSTD_estimateCStreamSize() will provide a budget large enough for any compression level up to selected one.
- It will also consider src size to be arbitrarily "large", which is worst case.
- If srcSize is known to always be small, ZSTD_estimateCStreamSize_usingCParams() can provide a tighter estimation.
- ZSTD_estimateCStreamSize_usingCParams() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel.
- ZSTD_estimateCStreamSize_usingCCtxParams() can be used in tandem with ZSTD_CCtxParam_setParameter(). Only single-threaded compression is supported. This function will return an error code if ZSTD_p_nbWorkers is >= 1.
- Note : CStream size estimation is only correct for single-threaded compression.
- ZSTD_DStream memory budget depends on window Size.
- This information can be passed manually, using ZSTD_estimateDStreamSize,
- or deducted from a valid frame Header, using ZSTD_estimateDStreamSize_fromFrame();
- Note : if streaming is init with function ZSTD_init?Stream_usingDict(),
- an internal ?Dict will be created, which additional size is not estimated here.
- In this case, get total size by adding ZSTD_estimate?DictSize
-</p></pre><BR>
-
-<pre><b>size_t ZSTD_estimateCDictSize(size_t dictSize, int compressionLevel);
-size_t ZSTD_estimateCDictSize_advanced(size_t dictSize, ZSTD_compressionParameters cParams, ZSTD_dictLoadMethod_e dictLoadMethod);
-size_t ZSTD_estimateDDictSize(size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod);
-</b><p> ZSTD_estimateCDictSize() will bet that src size is relatively "small", and content is copied, like ZSTD_createCDict().
- ZSTD_estimateCDictSize_advanced() makes it possible to control compression parameters precisely, like ZSTD_createCDict_advanced().
- Note : dictionaries created by reference (`ZSTD_dlm_byRef`) are logically smaller.
-
-</p></pre><BR>
-
-<pre><b>ZSTD_CCtx* ZSTD_initStaticCCtx(void* workspace, size_t workspaceSize);
-ZSTD_CStream* ZSTD_initStaticCStream(void* workspace, size_t workspaceSize); </b>/**< same as ZSTD_initStaticCCtx() */<b>
-</b><p> Initialize an object using a pre-allocated fixed-size buffer.
- workspace: The memory area to emplace the object into.
- Provided pointer *must be 8-bytes aligned*.
- Buffer must outlive object.
- workspaceSize: Use ZSTD_estimate*Size() to determine
- how large workspace must be to support target scenario.
- @return : pointer to object (same address as workspace, just different type),
- or NULL if error (size too small, incorrect alignment, etc.)
- Note : zstd will never resize nor malloc() when using a static buffer.
- If the object requires more memory than available,
- zstd will just error out (typically ZSTD_error_memory_allocation).
- Note 2 : there is no corresponding "free" function.
- Since workspace is allocated externally, it must be freed externally too.
- Note 3 : cParams : use ZSTD_getCParams() to convert a compression level
- into its associated cParams.
- Limitation 1 : currently not compatible with internal dictionary creation, triggered by
- ZSTD_CCtx_loadDictionary(), ZSTD_initCStream_usingDict() or ZSTD_initDStream_usingDict().
- Limitation 2 : static cctx currently not compatible with multi-threading.
- Limitation 3 : static dctx is incompatible with legacy support.
-
-</p></pre><BR>
-
-<pre><b>ZSTD_DStream* ZSTD_initStaticDStream(void* workspace, size_t workspaceSize); </b>/**< same as ZSTD_initStaticDCtx() */<b>
-</b></pre><BR>
-<pre><b>typedef void* (*ZSTD_allocFunction) (void* opaque, size_t size);
-typedef void (*ZSTD_freeFunction) (void* opaque, void* address);
-typedef struct { ZSTD_allocFunction customAlloc; ZSTD_freeFunction customFree; void* opaque; } ZSTD_customMem;
-static ZSTD_customMem const ZSTD_defaultCMem = { NULL, NULL, NULL }; </b>/**< this constant defers to stdlib's functions */<b>
-</b><p> These prototypes make it possible to pass your own allocation/free functions.
- ZSTD_customMem is provided at creation time, using ZSTD_create*_advanced() variants listed below.
- All allocation/free operations will be completed using these custom variants instead of regular <stdlib.h> ones.
-
-</p></pre><BR>
-
-<a name="Chapter17"></a><h2>Advanced compression functions</h2><pre></pre>
-
-<pre><b>ZSTD_CDict* ZSTD_createCDict_byReference(const void* dictBuffer, size_t dictSize, int compressionLevel);
-</b><p> Create a digested dictionary for compression
- Dictionary content is simply referenced, and therefore stays in dictBuffer.
- It is important that dictBuffer outlives CDict, it must remain read accessible throughout the lifetime of CDict
-</p></pre><BR>
-
-<pre><b>ZSTD_compressionParameters ZSTD_getCParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize);
-</b><p> @return ZSTD_compressionParameters structure for a selected compression level and estimated srcSize.
- `estimatedSrcSize` value is optional, select 0 if not known
-</p></pre><BR>
-
-<pre><b>ZSTD_parameters ZSTD_getParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize);
-</b><p> same as ZSTD_getCParams(), but @return a full `ZSTD_parameters` object instead of sub-component `ZSTD_compressionParameters`.
- All fields of `ZSTD_frameParameters` are set to default : contentSize=1, checksum=0, noDictID=0
-</p></pre><BR>
-
-<pre><b>size_t ZSTD_checkCParams(ZSTD_compressionParameters params);
-</b><p> Ensure param values remain within authorized range
-</p></pre><BR>
-
-<pre><b>ZSTD_compressionParameters ZSTD_adjustCParams(ZSTD_compressionParameters cPar, unsigned long long srcSize, size_t dictSize);
-</b><p> optimize params for a given `srcSize` and `dictSize`.
- both values are optional, select `0` if unknown.
-</p></pre><BR>
-
-<pre><b>size_t ZSTD_compress_advanced (ZSTD_CCtx* cctx,
- void* dst, size_t dstCapacity,
- const void* src, size_t srcSize,
- const void* dict,size_t dictSize,
- ZSTD_parameters params);
-</b><p> Same as ZSTD_compress_usingDict(), with fine-tune control over each compression parameter
-</p></pre><BR>
-
-<pre><b>size_t ZSTD_compress_usingCDict_advanced(ZSTD_CCtx* cctx,
- void* dst, size_t dstCapacity,
- const void* src, size_t srcSize,
- const ZSTD_CDict* cdict, ZSTD_frameParameters fParams);
-</b><p> Same as ZSTD_compress_usingCDict(), with fine-tune control over frame parameters
-</p></pre><BR>
-
-<a name="Chapter18"></a><h2>Advanced decompression functions</h2><pre></pre>
-
-<pre><b>unsigned ZSTD_isFrame(const void* buffer, size_t size);
-</b><p> Tells if the content of `buffer` starts with a valid Frame Identifier.
- Note : Frame Identifier is 4 bytes. If `size < 4`, @return will always be 0.
- Note 2 : Legacy Frame Identifiers are considered valid only if Legacy Support is enabled.
- Note 3 : Skippable Frame Identifiers are considered valid.
-</p></pre><BR>
-
-<pre><b>ZSTD_DDict* ZSTD_createDDict_byReference(const void* dictBuffer, size_t dictSize);
-</b><p> Create a digested dictionary, ready to start decompression operation without startup delay.
- Dictionary content is referenced, and therefore stays in dictBuffer.
- It is important that dictBuffer outlives DDict,
- it must remain read accessible throughout the lifetime of DDict
-</p></pre><BR>
-
-<pre><b>unsigned ZSTD_getDictID_fromDict(const void* dict, size_t dictSize);
-</b><p> Provides the dictID stored within dictionary.
- if @return == 0, the dictionary is not conformant with Zstandard specification.
- It can still be loaded, but as a content-only dictionary.
-</p></pre><BR>
-
-<pre><b>unsigned ZSTD_getDictID_fromDDict(const ZSTD_DDict* ddict);
-</b><p> Provides the dictID of the dictionary loaded into `ddict`.
- If @return == 0, the dictionary is not conformant to Zstandard specification, or empty.
- Non-conformant dictionaries can still be loaded, but as content-only dictionaries.
-</p></pre><BR>
-
-<pre><b>unsigned ZSTD_getDictID_fromFrame(const void* src, size_t srcSize);
-</b><p> Provides the dictID required to decompressed the frame stored within `src`.
- If @return == 0, the dictID could not be decoded.
- This could for one of the following reasons :
- - The frame does not require a dictionary to be decoded (most common case).
- - The frame was built with dictID intentionally removed. Whatever dictionary is necessary is a hidden information.
- Note : this use case also happens when using a non-conformant dictionary.
- - `srcSize` is too small, and as a result, the frame header could not be decoded (only possible if `srcSize < ZSTD_FRAMEHEADERSIZE_MAX`).
- - This is not a Zstandard frame.
- When identifying the exact failure cause, it's possible to use ZSTD_getFrameHeader(), which will provide a more precise error code.
-</p></pre><BR>
-
-<a name="Chapter19"></a><h2>Advanced streaming functions</h2><pre></pre>
-
-<h3>Advanced Streaming compression functions</h3><pre></pre><b><pre>size_t ZSTD_initCStream_srcSize(ZSTD_CStream* zcs, int compressionLevel, unsigned long long pledgedSrcSize); </b>/**< pledgedSrcSize must be correct. If it is not known at init time, use ZSTD_CONTENTSIZE_UNKNOWN. Note that, for compatibility with older programs, "0" also disables frame content size field. It may be enabled in the future. */<b>
-size_t ZSTD_initCStream_usingDict(ZSTD_CStream* zcs, const void* dict, size_t dictSize, int compressionLevel); </b>/**< creates of an internal CDict (incompatible with static CCtx), except if dict == NULL or dictSize < 8, in which case no dict is used. Note: dict is loaded with ZSTD_dm_auto (treated as a full zstd dictionary if it begins with ZSTD_MAGIC_DICTIONARY, else as raw content) and ZSTD_dlm_byCopy.*/<b>
-size_t ZSTD_initCStream_advanced(ZSTD_CStream* zcs, const void* dict, size_t dictSize,
- ZSTD_parameters params, unsigned long long pledgedSrcSize); </b>/**< pledgedSrcSize must be correct. If srcSize is not known at init time, use value ZSTD_CONTENTSIZE_UNKNOWN. dict is loaded with ZSTD_dm_auto and ZSTD_dlm_byCopy. */<b>
-size_t ZSTD_initCStream_usingCDict(ZSTD_CStream* zcs, const ZSTD_CDict* cdict); </b>/**< note : cdict will just be referenced, and must outlive compression session */<b>
-size_t ZSTD_initCStream_usingCDict_advanced(ZSTD_CStream* zcs, const ZSTD_CDict* cdict, ZSTD_frameParameters fParams, unsigned long long pledgedSrcSize); </b>/**< same as ZSTD_initCStream_usingCDict(), with control over frame parameters. pledgedSrcSize must be correct. If srcSize is not known at init time, use value ZSTD_CONTENTSIZE_UNKNOWN. */<b>
-</pre></b><BR>
-<pre><b>size_t ZSTD_resetCStream(ZSTD_CStream* zcs, unsigned long long pledgedSrcSize);
-</b><p> start a new compression job, using same parameters from previous job.
- This is typically useful to skip dictionary loading stage, since it will re-use it in-place.
- Note that zcs must be init at least once before using ZSTD_resetCStream().
- If pledgedSrcSize is not known at reset time, use macro ZSTD_CONTENTSIZE_UNKNOWN.
- If pledgedSrcSize > 0, its value must be correct, as it will be written in header, and controlled at the end.
- For the time being, pledgedSrcSize==0 is interpreted as "srcSize unknown" for compatibility with older programs,
- but it will change to mean "empty" in future version, so use macro ZSTD_CONTENTSIZE_UNKNOWN instead.
- @return : 0, or an error code (which can be tested using ZSTD_isError())
-
-</p></pre><BR>
-
-<pre><b>typedef struct {
- unsigned long long ingested; </b>/* nb input bytes read and buffered */<b>
- unsigned long long consumed; </b>/* nb input bytes actually compressed */<b>
- unsigned long long produced; </b>/* nb of compressed bytes generated and buffered */<b>
- unsigned long long flushed; </b>/* nb of compressed bytes flushed : not provided; can be tracked from caller side */<b>
- unsigned currentJobID; </b>/* MT only : latest started job nb */<b>
- unsigned nbActiveWorkers; </b>/* MT only : nb of workers actively compressing at probe time */<b>
-} ZSTD_frameProgression;
-</b></pre><BR>
-<pre><b>size_t ZSTD_toFlushNow(ZSTD_CCtx* cctx);
-</b><p> Tell how many bytes are ready to be flushed immediately.
- Useful for multithreading scenarios (nbWorkers >= 1).
- Probe the oldest active job, defined as oldest job not yet entirely flushed,
- and check its output buffer.
- @return : amount of data stored in oldest job and ready to be flushed immediately.
- if @return == 0, it means either :
- + there is no active job (could be checked with ZSTD_frameProgression()), or
- + oldest job is still actively compressing data,
- but everything it has produced has also been flushed so far,
- therefore flush speed is limited by production speed of oldest job
- irrespective of the speed of concurrent (and newer) jobs.
-
-</p></pre><BR>
-
-<h3>Advanced Streaming decompression functions</h3><pre></pre><b><pre>size_t ZSTD_initDStream_usingDict(ZSTD_DStream* zds, const void* dict, size_t dictSize); </b>/**< note: no dictionary will be used if dict == NULL or dictSize < 8 */<b>
-size_t ZSTD_initDStream_usingDDict(ZSTD_DStream* zds, const ZSTD_DDict* ddict); </b>/**< note : ddict is referenced, it must outlive decompression session */<b>
-size_t ZSTD_resetDStream(ZSTD_DStream* zds); </b>/**< re-use decompression parameters from previous init; saves dictionary loading */<b>
-</pre></b><BR>
-<a name="Chapter20"></a><h2>Buffer-less and synchronous inner streaming functions</h2><pre>
- This is an advanced API, giving full control over buffer management, for users which need direct control over memory.
- But it's also a complex one, with several restrictions, documented below.
- Prefer normal streaming API for an easier experience.
-
-<BR></pre>
-
-<a name="Chapter21"></a><h2>Buffer-less streaming compression (synchronous mode)</h2><pre>
- A ZSTD_CCtx object is required to track streaming operations.
- Use ZSTD_createCCtx() / ZSTD_freeCCtx() to manage resource.
- ZSTD_CCtx object can be re-used multiple times within successive compression operations.
-
- Start by initializing a context.
- Use ZSTD_compressBegin(), or ZSTD_compressBegin_usingDict() for dictionary compression,
- or ZSTD_compressBegin_advanced(), for finer parameter control.
- It's also possible to duplicate a reference context which has already been initialized, using ZSTD_copyCCtx()
-
- Then, consume your input using ZSTD_compressContinue().
- There are some important considerations to keep in mind when using this advanced function :
- - ZSTD_compressContinue() has no internal buffer. It uses externally provided buffers only.
- - Interface is synchronous : input is consumed entirely and produces 1+ compressed blocks.
- - Caller must ensure there is enough space in `dst` to store compressed data under worst case scenario.
- Worst case evaluation is provided by ZSTD_compressBound().
- ZSTD_compressContinue() doesn't guarantee recover after a failed compression.
- - ZSTD_compressContinue() presumes prior input ***is still accessible and unmodified*** (up to maximum distance size, see WindowLog).
- It remembers all previous contiguous blocks, plus one separated memory segment (which can itself consists of multiple contiguous blocks)
- - ZSTD_compressContinue() detects that prior input has been overwritten when `src` buffer overlaps.
- In which case, it will "discard" the relevant memory section from its history.
-
- Finish a frame with ZSTD_compressEnd(), which will write the last block(s) and optional checksum.
- It's possible to use srcSize==0, in which case, it will write a final empty block to end the frame.
- Without last block mark, frames are considered unfinished (hence corrupted) by compliant decoders.
-
- `ZSTD_CCtx` object can be re-used (ZSTD_compressBegin()) to compress again.
-<BR></pre>
-
-<h3>Buffer-less streaming compression functions</h3><pre></pre><b><pre>size_t ZSTD_compressBegin(ZSTD_CCtx* cctx, int compressionLevel);
-size_t ZSTD_compressBegin_usingDict(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, int compressionLevel);
-size_t ZSTD_compressBegin_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_parameters params, unsigned long long pledgedSrcSize); </b>/**< pledgedSrcSize : If srcSize is not known at init time, use ZSTD_CONTENTSIZE_UNKNOWN */<b>
-size_t ZSTD_compressBegin_usingCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict); </b>/**< note: fails if cdict==NULL */<b>
-size_t ZSTD_compressBegin_usingCDict_advanced(ZSTD_CCtx* const cctx, const ZSTD_CDict* const cdict, ZSTD_frameParameters const fParams, unsigned long long const pledgedSrcSize); </b>/* compression parameters are already set within cdict. pledgedSrcSize must be correct. If srcSize is not known, use macro ZSTD_CONTENTSIZE_UNKNOWN */<b>
-size_t ZSTD_copyCCtx(ZSTD_CCtx* cctx, const ZSTD_CCtx* preparedCCtx, unsigned long long pledgedSrcSize); </b>/**< note: if pledgedSrcSize is not known, use ZSTD_CONTENTSIZE_UNKNOWN */<b>
-</pre></b><BR>
-<a name="Chapter22"></a><h2>Buffer-less streaming decompression (synchronous mode)</h2><pre>
- A ZSTD_DCtx object is required to track streaming operations.
- Use ZSTD_createDCtx() / ZSTD_freeDCtx() to manage it.
- A ZSTD_DCtx object can be re-used multiple times.
-
- First typical operation is to retrieve frame parameters, using ZSTD_getFrameHeader().
- Frame header is extracted from the beginning of compressed frame, so providing only the frame's beginning is enough.
- Data fragment must be large enough to ensure successful decoding.
- `ZSTD_frameHeaderSize_max` bytes is guaranteed to always be large enough.
- @result : 0 : successful decoding, the `ZSTD_frameHeader` structure is correctly filled.
- >0 : `srcSize` is too small, please provide at least @result bytes on next attempt.
- errorCode, which can be tested using ZSTD_isError().
-
- It fills a ZSTD_frameHeader structure with important information to correctly decode the frame,
- such as the dictionary ID, content size, or maximum back-reference distance (`windowSize`).
- Note that these values could be wrong, either because of data corruption, or because a 3rd party deliberately spoofs false information.
- As a consequence, check that values remain within valid application range.
- For example, do not allocate memory blindly, check that `windowSize` is within expectation.
- Each application can set its own limits, depending on local restrictions.
- For extended interoperability, it is recommended to support `windowSize` of at least 8 MB.
-
- ZSTD_decompressContinue() needs previous data blocks during decompression, up to `windowSize` bytes.
- ZSTD_decompressContinue() is very sensitive to contiguity,
- if 2 blocks don't follow each other, make sure that either the compressor breaks contiguity at the same place,
- or that previous contiguous segment is large enough to properly handle maximum back-reference distance.
- There are multiple ways to guarantee this condition.
-
- The most memory efficient way is to use a round buffer of sufficient size.
- Sufficient size is determined by invoking ZSTD_decodingBufferSize_min(),
- which can @return an error code if required value is too large for current system (in 32-bits mode).
- In a round buffer methodology, ZSTD_decompressContinue() decompresses each block next to previous one,
- up to the moment there is not enough room left in the buffer to guarantee decoding another full block,
- which maximum size is provided in `ZSTD_frameHeader` structure, field `blockSizeMax`.
- At which point, decoding can resume from the beginning of the buffer.
- Note that already decoded data stored in the buffer should be flushed before being overwritten.
-
- There are alternatives possible, for example using two or more buffers of size `windowSize` each, though they consume more memory.
-
- Finally, if you control the compression process, you can also ignore all buffer size rules,
- as long as the encoder and decoder progress in "lock-step",
- aka use exactly the same buffer sizes, break contiguity at the same place, etc.
-
- Once buffers are setup, start decompression, with ZSTD_decompressBegin().
- If decompression requires a dictionary, use ZSTD_decompressBegin_usingDict() or ZSTD_decompressBegin_usingDDict().
-
- Then use ZSTD_nextSrcSizeToDecompress() and ZSTD_decompressContinue() alternatively.
- ZSTD_nextSrcSizeToDecompress() tells how many bytes to provide as 'srcSize' to ZSTD_decompressContinue().
- ZSTD_decompressContinue() requires this _exact_ amount of bytes, or it will fail.
-
- @result of ZSTD_decompressContinue() is the number of bytes regenerated within 'dst' (necessarily <= dstCapacity).
- It can be zero : it just means ZSTD_decompressContinue() has decoded some metadata item.
- It can also be an error code, which can be tested with ZSTD_isError().
-
- A frame is fully decoded when ZSTD_nextSrcSizeToDecompress() returns zero.
- Context can then be reset to start a new decompression.
-
- Note : it's possible to know if next input to present is a header or a block, using ZSTD_nextInputType().
- This information is not required to properly decode a frame.
-
- == Special case : skippable frames
-
- Skippable frames allow integration of user-defined data into a flow of concatenated frames.
- Skippable frames will be ignored (skipped) by decompressor.
- The format of skippable frames is as follows :
- a) Skippable frame ID - 4 Bytes, Little endian format, any value from 0x184D2A50 to 0x184D2A5F
- b) Frame Size - 4 Bytes, Little endian format, unsigned 32-bits
- c) Frame Content - any content (User Data) of length equal to Frame Size
- For skippable frames ZSTD_getFrameHeader() returns zfhPtr->frameType==ZSTD_skippableFrame.
- For skippable frames ZSTD_decompressContinue() always returns 0 : it only skips the content.
-<BR></pre>
-
-<h3>Buffer-less streaming decompression functions</h3><pre></pre><b><pre>typedef enum { ZSTD_frame, ZSTD_skippableFrame } ZSTD_frameType_e;
-typedef struct {
- unsigned long long frameContentSize; </b>/* if == ZSTD_CONTENTSIZE_UNKNOWN, it means this field is not available. 0 means "empty" */<b>
- unsigned long long windowSize; </b>/* can be very large, up to <= frameContentSize */<b>
- unsigned blockSizeMax;
- ZSTD_frameType_e frameType; </b>/* if == ZSTD_skippableFrame, frameContentSize is the size of skippable content */<b>
- unsigned headerSize;
- unsigned dictID;
- unsigned checksumFlag;
-} ZSTD_frameHeader;
-</b>/** ZSTD_getFrameHeader() :<b>
- * decode Frame Header, or requires larger `srcSize`.
- * @return : 0, `zfhPtr` is correctly filled,
- * >0, `srcSize` is too small, value is wanted `srcSize` amount,
- * or an error code, which can be tested using ZSTD_isError() */
-size_t ZSTD_getFrameHeader(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize); </b>/**< doesn't consume input */<b>
-size_t ZSTD_decodingBufferSize_min(unsigned long long windowSize, unsigned long long frameContentSize); </b>/**< when frame content size is not known, pass in frameContentSize == ZSTD_CONTENTSIZE_UNKNOWN */<b>
-</pre></b><BR>
-<pre><b>typedef enum { ZSTDnit_frameHeader, ZSTDnit_blockHeader, ZSTDnit_block, ZSTDnit_lastBlock, ZSTDnit_checksum, ZSTDnit_skippableFrame } ZSTD_nextInputType_e;
-</b></pre><BR>
-<a name="Chapter23"></a><h2>New advanced API (experimental)</h2><pre></pre>
+<a name="Chapter14"></a><h2>Advanced compression API</h2><pre></pre>
<pre><b>typedef enum {
</b>/* Opened question : should we have a format ZSTD_f_auto ?<b>
* Since meaning is a little different, another option could be to define different enums for compression and decompression.
* This question could be kept for later, when there are actually multiple formats to support,
* but there is also the question of pinning enum values, and pinning value `0` is especially important */
- ZSTD_f_zstd1 = 0, </b>/* zstd frame format, specified in zstd_compression_format.md (default) */<b>
- ZSTD_f_zstd1_magicless, </b>/* Variant of zstd frame format, without initial 4-bytes magic number.<b>
- * Useful to save 4 bytes per generated frame.
- * Decoder cannot recognise automatically this format, requiring instructions. */
+ ZSTD_f_zstd1 = 0, </b>/* zstd frame format, specified in zstd_compression_format.md (default) */<b>
+ ZSTD_f_zstd1_magicless = 1, </b>/* Variant of zstd frame format, without initial 4-bytes magic number.<b>
+ * Useful to save 4 bytes per generated frame.
+ * Decoder cannot recognise automatically this format, requiring instructions. */
} ZSTD_format_e;
</b></pre><BR>
+<pre><b>typedef enum { ZSTD_fast=1,
+ ZSTD_dfast=2,
+ ZSTD_greedy=3,
+ ZSTD_lazy=4,
+ ZSTD_lazy2=5,
+ ZSTD_btlazy2=6,
+ ZSTD_btopt=7,
+ ZSTD_btultra=8
+ </b>/* note : new strategies might be added in the future */<b>
+ } ZSTD_strategy;
+</b></pre><BR>
<pre><b>typedef enum {
</b>/* Note: this enum and the behavior it controls are effectively internal<b>
* implementation details of the compressor. They are expected to continue
} ZSTD_dictAttachPref_e;
</b></pre><BR>
<pre><b>typedef enum {
- </b>/* compression format */<b>
- ZSTD_p_format = 10, </b>/* See ZSTD_format_e enum definition.<b>
- * Cast selected format as unsigned for ZSTD_CCtx_setParameter() compatibility. */
</b>/* compression parameters */<b>
ZSTD_p_compressionLevel=100, </b>/* Update all compression parameters according to pre-defined cLevel table<b>
* Note 1 : it's possible to pass a negative compression level by casting it to unsigned type.
* Note 2 : setting a level sets all default values of other compression parameters.
* Note 3 : setting compressionLevel automatically updates ZSTD_p_compressLiterals. */
- ZSTD_p_windowLog, </b>/* Maximum allowed back-reference distance, expressed as power of 2.<b>
+ ZSTD_p_windowLog=101, </b>/* Maximum allowed back-reference distance, expressed as power of 2.<b>
* Must be clamped between ZSTD_WINDOWLOG_MIN and ZSTD_WINDOWLOG_MAX.
* Special: value 0 means "use default windowLog".
* Note: Using a window size greater than ZSTD_MAXWINDOWSIZE_DEFAULT (default: 2^27)
* requires explicitly allowing such window size during decompression stage. */
- ZSTD_p_hashLog, </b>/* Size of the initial probe table, as a power of 2.<b>
+ ZSTD_p_hashLog=102, </b>/* Size of the initial probe table, as a power of 2.<b>
* Resulting table size is (1 << (hashLog+2)).
* Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX.
* Larger tables improve compression ratio of strategies <= dFast,
* and improve speed of strategies > dFast.
* Special: value 0 means "use default hashLog". */
- ZSTD_p_chainLog, </b>/* Size of the multi-probe search table, as a power of 2.<b>
+ ZSTD_p_chainLog=103, </b>/* Size of the multi-probe search table, as a power of 2.<b>
* Resulting table size is (1 << (chainLog+2)).
* Must be clamped between ZSTD_CHAINLOG_MIN and ZSTD_CHAINLOG_MAX.
* Larger tables result in better and slower compression.
* Note it's still useful when using "dfast" strategy,
* in which case it defines a secondary probe table.
* Special: value 0 means "use default chainLog". */
- ZSTD_p_searchLog, </b>/* Number of search attempts, as a power of 2.<b>
+ ZSTD_p_searchLog=104, </b>/* Number of search attempts, as a power of 2.<b>
* More attempts result in better and slower compression.
* This parameter is useless when using "fast" and "dFast" strategies.
* Special: value 0 means "use default searchLog". */
- ZSTD_p_minMatch, </b>/* Minimum size of searched matches (note : repCode matches can be smaller).<b>
+ ZSTD_p_minMatch=105, </b>/* Minimum size of searched matches (note : repCode matches can be smaller).<b>
* Larger values make faster compression and decompression, but decrease ratio.
* Must be clamped between ZSTD_SEARCHLENGTH_MIN and ZSTD_SEARCHLENGTH_MAX.
* Note that currently, for all strategies < btopt, effective minimum is 4.
* , for all strategies > fast, effective maximum is 6.
* Special: value 0 means "use default minMatchLength". */
- ZSTD_p_targetLength, </b>/* Impact of this field depends on strategy.<b>
+ ZSTD_p_targetLength=106, </b>/* Impact of this field depends on strategy.<b>
* For strategies btopt & btultra:
* Length of Match considered "good enough" to stop search.
* Larger values make compression stronger, and slower.
* Distance between match sampling.
* Larger values make compression faster, and weaker.
* Special: value 0 means "use default targetLength". */
- ZSTD_p_compressionStrategy, </b>/* See ZSTD_strategy enum definition.<b>
+ ZSTD_p_compressionStrategy=107, </b>/* See ZSTD_strategy enum definition.<b>
* Cast selected strategy as unsigned for ZSTD_CCtx_setParameter() compatibility.
* The higher the value of selected strategy, the more complex it is,
* resulting in stronger and slower compression.
* Special: value 0 means "use default strategy". */
+ </b>/* LDM mode parameters */<b>
ZSTD_p_enableLongDistanceMatching=160, </b>/* Enable long distance matching.<b>
- * This parameter is designed to improve compression ratio
- * for large inputs, by finding large matches at long distance.
- * It increases memory usage and window size.
- * Note: enabling this parameter increases ZSTD_p_windowLog to 128 MB
- * except when expressly set to a different value. */
- ZSTD_p_ldmHashLog, </b>/* Size of the table for long distance matching, as a power of 2.<b>
+ * This parameter is designed to improve compression ratio
+ * for large inputs, by finding large matches at long distance.
+ * It increases memory usage and window size.
+ * Note: enabling this parameter increases ZSTD_p_windowLog to 128 MB
+ * except when expressly set to a different value. */
+ ZSTD_p_ldmHashLog=161, </b>/* Size of the table for long distance matching, as a power of 2.<b>
* Larger values increase memory usage and compression ratio,
* but decrease compression speed.
* Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX
* default: windowlog - 7.
* Special: value 0 means "automatically determine hashlog". */
- ZSTD_p_ldmMinMatch, </b>/* Minimum match size for long distance matcher.<b>
+ ZSTD_p_ldmMinMatch=162, </b>/* Minimum match size for long distance matcher.<b>
* Larger/too small values usually decrease compression ratio.
* Must be clamped between ZSTD_LDM_MINMATCH_MIN and ZSTD_LDM_MINMATCH_MAX.
* Special: value 0 means "use default value" (default: 64). */
- ZSTD_p_ldmBucketSizeLog, </b>/* Log size of each bucket in the LDM hash table for collision resolution.<b>
+ ZSTD_p_ldmBucketSizeLog=163, </b>/* Log size of each bucket in the LDM hash table for collision resolution.<b>
* Larger values improve collision resolution but decrease compression speed.
* The maximum value is ZSTD_LDM_BUCKETSIZELOG_MAX .
* Special: value 0 means "use default value" (default: 3). */
- ZSTD_p_ldmHashEveryLog, </b>/* Frequency of inserting/looking up entries in the LDM hash table.<b>
+ ZSTD_p_ldmHashEveryLog=164, </b>/* Frequency of inserting/looking up entries into the LDM hash table.<b>
* Must be clamped between 0 and (ZSTD_WINDOWLOG_MAX - ZSTD_HASHLOG_MIN).
* Default is MAX(0, (windowLog - ldmHashLog)), optimizing hash table usage.
* Larger values improve compression speed.
ZSTD_p_contentSizeFlag=200, </b>/* Content size will be written into frame header _whenever known_ (default:1)<b>
* Content size must be known at the beginning of compression,
* it is provided using ZSTD_CCtx_setPledgedSrcSize() */
- ZSTD_p_checksumFlag, </b>/* A 32-bits checksum of content is written at end of frame (default:0) */<b>
- ZSTD_p_dictIDFlag, </b>/* When applicable, dictionary's ID is written into frame header (default:1) */<b>
+ ZSTD_p_checksumFlag=201, </b>/* A 32-bits checksum of content is written at end of frame (default:0) */<b>
+ ZSTD_p_dictIDFlag=202, </b>/* When applicable, dictionary's ID is written into frame header (default:1) */<b>
</b>/* multi-threading parameters */<b>
</b>/* These parameters are only useful if multi-threading is enabled (ZSTD_MULTITHREAD).<b>
* (note : a strong exception to this rule is when first invocation sets ZSTD_e_end : it becomes a blocking call).
* More workers improve speed, but also increase memory usage.
* Default value is `0`, aka "single-threaded mode" : no worker is spawned, compression is performed inside Caller's thread, all invocations are blocking */
- ZSTD_p_jobSize, </b>/* Size of a compression job. This value is enforced only in non-blocking mode.<b>
+ ZSTD_p_jobSize=401, </b>/* Size of a compression job. This value is enforced only in non-blocking mode.<b>
* Each compression job is completed in parallel, so this value indirectly controls the nb of active threads.
* 0 means default, which is dynamically determined based on compression parameters.
* Job size must be a minimum of overlapSize, or 1 MB, whichever is largest.
* The minimum size is automatically and transparently enforced */
- ZSTD_p_overlapSizeLog, </b>/* Size of previous input reloaded at the beginning of each job.<b>
+ ZSTD_p_overlapSizeLog=402, </b>/* Size of previous input reloaded at the beginning of each job.<b>
* 0 => no overlap, 6(default) => use 1/8th of windowSize, >=9 => use full windowSize */
</b>/* =================================================================== */<b>
</b>/* experimental parameters - no stability guaranteed */<b>
+ </b>/* note : should this be exported in a different section of zstd.h ? */<b>
</b>/* =================================================================== */<b>
+ </b>/* compression format */<b>
+ ZSTD_p_format = 10, </b>/* See ZSTD_format_e enum definition.<b>
+ * Cast selected format as unsigned for ZSTD_CCtx_setParameter() compatibility. */
+
ZSTD_p_forceMaxWindow=1100, </b>/* Force back-reference distances to remain < windowSize,<b>
* even when referencing into Dictionary content (default:0) */
ZSTD_p_forceAttachDict, </b>/* Controls whether the contents of a CDict are<b>
<pre><b>size_t ZSTD_CCtx_setParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, unsigned value);
</b><p> Set one compression parameter, selected by enum ZSTD_cParameter.
Setting a parameter is generally only possible during frame initialization (before starting compression).
- Exception : when using multi-threading mode (nbThreads >= 1),
- following parameters can be updated _during_ compression (within same frame):
+ Exception : when using multi-threading mode (nbWorkers >= 1),
+ the following parameters can be updated _during_ compression (within same frame):
=> compressionLevel, hashLog, chainLog, searchLog, minMatch, targetLength and strategy.
- new parameters will be active on next job, or after a flush().
- Note : when `value` type is not unsigned (int, or enum), cast it to unsigned for proper type checking.
- @result : informational value (typically, value being set, correctly clamped),
+ new parameters will be active for next job only (after a flush()).
+ Note : when original `value` type is not unsigned (like int, or enum), cast it to unsigned.
+ @result : informational value (typically, value being effectively set, after clamping),
or an error code (which can be tested with ZSTD_isError()).
</p></pre><BR>
<pre><b>size_t ZSTD_CCtx_setPledgedSrcSize(ZSTD_CCtx* cctx, unsigned long long pledgedSrcSize);
</b><p> Total input data size to be compressed as a single frame.
- This value will be controlled at the end, and result in error if not respected.
+ This value will be controlled at end of frame, and trigger an error if not respected.
@result : 0, or an error code (which can be tested with ZSTD_isError()).
Note 1 : 0 means zero, empty.
In order to mean "unknown content size", pass constant ZSTD_CONTENTSIZE_UNKNOWN.
ZSTD_CONTENTSIZE_UNKNOWN is default value for any new compression job.
Note 2 : If all data is provided and consumed in a single round,
- this value is overriden by srcSize instead.
+ this value is automatically overriden by srcSize instead.
</p></pre><BR>
<pre><b>size_t ZSTD_CCtx_loadDictionary(ZSTD_CCtx* cctx, const void* dict, size_t dictSize);
-size_t ZSTD_CCtx_loadDictionary_byReference(ZSTD_CCtx* cctx, const void* dict, size_t dictSize);
-size_t ZSTD_CCtx_loadDictionary_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictContentType_e dictContentType);
</b><p> Create an internal CDict from `dict` buffer.
Decompression will have to use same dictionary.
@result : 0, or an error code (which can be tested with ZSTD_isError()).
<pre><b>size_t ZSTD_CCtx_refPrefix(ZSTD_CCtx* cctx,
const void* prefix, size_t prefixSize);
-size_t ZSTD_CCtx_refPrefix_advanced(ZSTD_CCtx* cctx,
- const void* prefix, size_t prefixSize,
- ZSTD_dictContentType_e dictContentType);
</b><p> Reference a prefix (single-usage dictionary) for next compression job.
Decompression will need same prefix to properly regenerate data.
Compressing with a prefix is similar in outcome as performing a diff and compressing it,
Note 3 : Referencing a prefix involves building tables, which are dependent on compression parameters.
It's a CPU consuming operation, with non-negligible impact on latency.
If there is a need to use same prefix multiple times, consider loadDictionary instead.
- Note 4 : By default, the prefix is treated as raw content (ZSTD_dm_rawContent).
- Use ZSTD_CCtx_refPrefix_advanced() to alter dictMode.
+ Note 4 : By default, the prefix is interpreted as raw content (ZSTD_dm_rawContent).
+ Use ZSTD_CCtx_refPrefix_advanced() to alter dictionary intepretation.
</p></pre><BR>
-<pre><b>void ZSTD_CCtx_reset(ZSTD_CCtx* cctx);
+<pre><b>typedef enum {
+ ZSTD_CCtx_reset_session_only = 1,
+ ZSTD_CCtx_reset_parameters = 2,
+ ZSTD_CCtx_reset_session_and_parameters = 3
+} ZSTD_CCtx_reset_directive;
+</b></pre><BR>
+<pre><b>size_t ZSTD_CCtx_reset(ZSTD_CCtx* cctx, ZSTD_CCtx_reset_directive zcrd);
</b><p> Return a CCtx to clean state.
- Useful after an error, or to interrupt an ongoing compression job and start a new one.
- Any internal data not yet flushed is cancelled.
- The parameters and dictionary are kept unchanged, to reset them use ZSTD_CCtx_resetParameters().
-
-</p></pre><BR>
-
-<pre><b>size_t ZSTD_CCtx_resetParameters(ZSTD_CCtx* cctx);
-</b><p> All parameters are back to default values (compression level is ZSTD_CLEVEL_DEFAULT).
- Dictionary (if any) is dropped.
- Resetting parameters is only possible during frame initialization (before starting compression).
- To reset the context use ZSTD_CCtx_reset().
- @return 0 or an error code (which can be checked with ZSTD_isError()).
+ There 2 things that can be reset, independently or jointly :
+ - The session : will stop compressing current frame, and stand ready to start a new one.
+ This action never fails.
+ Useful after an error, or to interrupt any ongoing compression.
+ Any internal data not yet flushed is cancelled.
+ But parameters and dictionary are kept unchanged.
+ Therefore, same parameters and dictionary will be used for next frame.
+ - The parameters : changes all parameters back to "default".
+ This removes any dictionary too.
+ Parameters can only be changed between 2 sessions (i.e. no compression is currently ongoing)
+ otherwise the reset fails, and function returns an error value (which can be tested using ZSTD_isError())
+ - Both : similar to resetting the session, followed by resetting parameters.
+ This action never fails.
</p></pre><BR>
</p></pre><BR>
-<pre><b>size_t ZSTD_compress_generic_simpleArgs (
- ZSTD_CCtx* cctx,
- void* dst, size_t dstCapacity, size_t* dstPos,
- const void* src, size_t srcSize, size_t* srcPos,
- ZSTD_EndDirective endOp);
-</b><p> Same as ZSTD_compress_generic(),
- but using only integral types as arguments.
- Argument list is larger than ZSTD_{in,out}Buffer,
- but can be helpful for binders from dynamic languages
- which have troubles handling structures containing memory pointers.
-
+<pre><b>size_t ZSTD_compress_generic_simpleArgs (
+ ZSTD_CCtx* cctx,
+ void* dst, size_t dstCapacity, size_t* dstPos,
+ const void* src, size_t srcSize, size_t* srcPos,
+ ZSTD_EndDirective endOp);
+</b><p> Same as ZSTD_compress_generic(),
+ but using only integral types as arguments.
+ Argument list is larger than ZSTD_{in,out}Buffer,
+ but can be helpful for binders from dynamic languages
+ which have troubles handling structures containing memory pointers.
+
+</p></pre><BR>
+
+<a name="Chapter15"></a><h2>experimental API (static linking only)</h2><pre>
+ The following symbols and constants
+ are not planned to join "stable API" status anytime soon.
+ Some will never reach "stable", and remain in the static_only section.
+ Some of them might be removed in the future.
+
+<BR></pre>
+
+<pre><b>typedef struct {
+ unsigned windowLog; </b>/**< largest match distance : larger == more compression, more memory needed during decompression */<b>
+ unsigned chainLog; </b>/**< fully searched segment : larger == more compression, slower, more memory (useless for fast) */<b>
+ unsigned hashLog; </b>/**< dispatch table : larger == faster, more memory */<b>
+ unsigned searchLog; </b>/**< nb of searches : larger == more compression, slower */<b>
+ unsigned searchLength; </b>/**< match length searched : larger == faster decompression, sometimes less compression */<b>
+ unsigned targetLength; </b>/**< acceptable match size for optimal parser (only) : larger == more compression, slower */<b>
+ ZSTD_strategy strategy; </b>/**< see ZSTD_strategy definition above */<b>
+} ZSTD_compressionParameters;
+</b></pre><BR>
+<pre><b>typedef struct {
+ unsigned contentSizeFlag; </b>/**< 1: content size will be in frame header (when known) */<b>
+ unsigned checksumFlag; </b>/**< 1: generate a 32-bits checksum using XXH64 algorithm at end of frame, for error detection */<b>
+ unsigned noDictIDFlag; </b>/**< 1: no dictID will be saved into frame header (dictID is only useful for dictionary compression) */<b>
+} ZSTD_frameParameters;
+</b></pre><BR>
+<pre><b>typedef struct {
+ ZSTD_compressionParameters cParams;
+ ZSTD_frameParameters fParams;
+} ZSTD_parameters;
+</b></pre><BR>
+<pre><b>typedef enum {
+ ZSTD_dct_auto = 0, </b>/* dictionary is "full" when starting with ZSTD_MAGIC_DICTIONARY, otherwise it is "rawContent" */<b>
+ ZSTD_dct_rawContent = 1, </b>/* ensures dictionary is always loaded as rawContent, even if it starts with ZSTD_MAGIC_DICTIONARY */<b>
+ ZSTD_dct_fullDict = 2 </b>/* refuses to load a dictionary if it does not respect Zstandard's specification, starting with ZSTD_MAGIC_DICTIONARY */<b>
+} ZSTD_dictContentType_e;
+</b></pre><BR>
+<pre><b>typedef enum {
+ ZSTD_dlm_byCopy = 0, </b>/**< Copy dictionary content internally */<b>
+ ZSTD_dlm_byRef = 1, </b>/**< Reference dictionary content -- the dictionary buffer must outlive its users. */<b>
+} ZSTD_dictLoadMethod_e;
+</b></pre><BR>
+<a name="Chapter16"></a><h2>Frame size functions</h2><pre></pre>
+
+<pre><b>size_t ZSTD_findFrameCompressedSize(const void* src, size_t srcSize);
+</b><p> `src` should point to the start of a ZSTD encoded frame or skippable frame
+ `srcSize` must be >= first frame size
+ @return : the compressed size of the first frame starting at `src`,
+ suitable to pass to `ZSTD_decompress` or similar,
+ or an error code if input is invalid
+</p></pre><BR>
+
+<pre><b>unsigned long long ZSTD_findDecompressedSize(const void* src, size_t srcSize);
+</b><p> `src` should point the start of a series of ZSTD encoded and/or skippable frames
+ `srcSize` must be the _exact_ size of this series
+ (i.e. there should be a frame boundary exactly at `srcSize` bytes after `src`)
+ @return : - decompressed size of all data in all successive frames
+ - if the decompressed size cannot be determined: ZSTD_CONTENTSIZE_UNKNOWN
+ - if an error occurred: ZSTD_CONTENTSIZE_ERROR
+
+ note 1 : decompressed size is an optional field, that may not be present, especially in streaming mode.
+ When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size.
+ In which case, it's necessary to use streaming mode to decompress data.
+ note 2 : decompressed size is always present when compression is done with ZSTD_compress()
+ note 3 : decompressed size can be very large (64-bits value),
+ potentially larger than what local system can handle as a single memory segment.
+ In which case, it's necessary to use streaming mode to decompress data.
+ note 4 : If source is untrusted, decompressed size could be wrong or intentionally modified.
+ Always ensure result fits within application's authorized limits.
+ Each application can set its own limits.
+ note 5 : ZSTD_findDecompressedSize handles multiple frames, and so it must traverse the input to
+ read each contained frame header. This is fast as most of the data is skipped,
+ however it does mean that all frame data must be present and valid.
+</p></pre><BR>
+
+<pre><b>size_t ZSTD_frameHeaderSize(const void* src, size_t srcSize);
+</b><p> srcSize must be >= ZSTD_frameHeaderSize_prefix.
+ @return : size of the Frame Header,
+ or an error code (if srcSize is too small)
+</p></pre><BR>
+
+<a name="Chapter17"></a><h2>Memory management</h2><pre></pre>
+
+<pre><b>size_t ZSTD_estimateCCtxSize(int compressionLevel);
+size_t ZSTD_estimateCCtxSize_usingCParams(ZSTD_compressionParameters cParams);
+size_t ZSTD_estimateCCtxSize_usingCCtxParams(const ZSTD_CCtx_params* params);
+size_t ZSTD_estimateDCtxSize(void);
+</b><p> These functions make it possible to estimate memory usage
+ of a future {D,C}Ctx, before its creation.
+ ZSTD_estimateCCtxSize() will provide a budget large enough for any compression level up to selected one.
+ It will also consider src size to be arbitrarily "large", which is worst case.
+ If srcSize is known to always be small, ZSTD_estimateCCtxSize_usingCParams() can provide a tighter estimation.
+ ZSTD_estimateCCtxSize_usingCParams() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel.
+ ZSTD_estimateCCtxSize_usingCCtxParams() can be used in tandem with ZSTD_CCtxParam_setParameter(). Only single-threaded compression is supported. This function will return an error code if ZSTD_p_nbWorkers is >= 1.
+ Note : CCtx size estimation is only correct for single-threaded compression.
+</p></pre><BR>
+
+<pre><b>size_t ZSTD_estimateCStreamSize(int compressionLevel);
+size_t ZSTD_estimateCStreamSize_usingCParams(ZSTD_compressionParameters cParams);
+size_t ZSTD_estimateCStreamSize_usingCCtxParams(const ZSTD_CCtx_params* params);
+size_t ZSTD_estimateDStreamSize(size_t windowSize);
+size_t ZSTD_estimateDStreamSize_fromFrame(const void* src, size_t srcSize);
+</b><p> ZSTD_estimateCStreamSize() will provide a budget large enough for any compression level up to selected one.
+ It will also consider src size to be arbitrarily "large", which is worst case.
+ If srcSize is known to always be small, ZSTD_estimateCStreamSize_usingCParams() can provide a tighter estimation.
+ ZSTD_estimateCStreamSize_usingCParams() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel.
+ ZSTD_estimateCStreamSize_usingCCtxParams() can be used in tandem with ZSTD_CCtxParam_setParameter(). Only single-threaded compression is supported. This function will return an error code if ZSTD_p_nbWorkers is >= 1.
+ Note : CStream size estimation is only correct for single-threaded compression.
+ ZSTD_DStream memory budget depends on window Size.
+ This information can be passed manually, using ZSTD_estimateDStreamSize,
+ or deducted from a valid frame Header, using ZSTD_estimateDStreamSize_fromFrame();
+ Note : if streaming is init with function ZSTD_init?Stream_usingDict(),
+ an internal ?Dict will be created, which additional size is not estimated here.
+ In this case, get total size by adding ZSTD_estimate?DictSize
+</p></pre><BR>
+
+<pre><b>size_t ZSTD_estimateCDictSize(size_t dictSize, int compressionLevel);
+size_t ZSTD_estimateCDictSize_advanced(size_t dictSize, ZSTD_compressionParameters cParams, ZSTD_dictLoadMethod_e dictLoadMethod);
+size_t ZSTD_estimateDDictSize(size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod);
+</b><p> ZSTD_estimateCDictSize() will bet that src size is relatively "small", and content is copied, like ZSTD_createCDict().
+ ZSTD_estimateCDictSize_advanced() makes it possible to control compression parameters precisely, like ZSTD_createCDict_advanced().
+ Note : dictionaries created by reference (`ZSTD_dlm_byRef`) are logically smaller.
+
+</p></pre><BR>
+
+<pre><b>ZSTD_CCtx* ZSTD_initStaticCCtx(void* workspace, size_t workspaceSize);
+ZSTD_CStream* ZSTD_initStaticCStream(void* workspace, size_t workspaceSize); </b>/**< same as ZSTD_initStaticCCtx() */<b>
+</b><p> Initialize an object using a pre-allocated fixed-size buffer.
+ workspace: The memory area to emplace the object into.
+ Provided pointer *must be 8-bytes aligned*.
+ Buffer must outlive object.
+ workspaceSize: Use ZSTD_estimate*Size() to determine
+ how large workspace must be to support target scenario.
+ @return : pointer to object (same address as workspace, just different type),
+ or NULL if error (size too small, incorrect alignment, etc.)
+ Note : zstd will never resize nor malloc() when using a static buffer.
+ If the object requires more memory than available,
+ zstd will just error out (typically ZSTD_error_memory_allocation).
+ Note 2 : there is no corresponding "free" function.
+ Since workspace is allocated externally, it must be freed externally too.
+ Note 3 : cParams : use ZSTD_getCParams() to convert a compression level
+ into its associated cParams.
+ Limitation 1 : currently not compatible with internal dictionary creation, triggered by
+ ZSTD_CCtx_loadDictionary(), ZSTD_initCStream_usingDict() or ZSTD_initDStream_usingDict().
+ Limitation 2 : static cctx currently not compatible with multi-threading.
+ Limitation 3 : static dctx is incompatible with legacy support.
+
+</p></pre><BR>
+
+<pre><b>ZSTD_DStream* ZSTD_initStaticDStream(void* workspace, size_t workspaceSize); </b>/**< same as ZSTD_initStaticDCtx() */<b>
+</b></pre><BR>
+<pre><b>typedef void* (*ZSTD_allocFunction) (void* opaque, size_t size);
+typedef void (*ZSTD_freeFunction) (void* opaque, void* address);
+typedef struct { ZSTD_allocFunction customAlloc; ZSTD_freeFunction customFree; void* opaque; } ZSTD_customMem;
+static ZSTD_customMem const ZSTD_defaultCMem = { NULL, NULL, NULL }; </b>/**< this constant defers to stdlib's functions */<b>
+</b><p> These prototypes make it possible to pass your own allocation/free functions.
+ ZSTD_customMem is provided at creation time, using ZSTD_create*_advanced() variants listed below.
+ All allocation/free operations will be completed using these custom variants instead of regular <stdlib.h> ones.
+
+</p></pre><BR>
+
+<a name="Chapter18"></a><h2>Advanced compression functions</h2><pre></pre>
+
+<pre><b>ZSTD_CDict* ZSTD_createCDict_byReference(const void* dictBuffer, size_t dictSize, int compressionLevel);
+</b><p> Create a digested dictionary for compression
+ Dictionary content is simply referenced, and therefore stays in dictBuffer.
+ It is important that dictBuffer outlives CDict, it must remain read accessible throughout the lifetime of CDict
+</p></pre><BR>
+
+<pre><b>ZSTD_compressionParameters ZSTD_getCParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize);
+</b><p> @return ZSTD_compressionParameters structure for a selected compression level and estimated srcSize.
+ `estimatedSrcSize` value is optional, select 0 if not known
+</p></pre><BR>
+
+<pre><b>ZSTD_parameters ZSTD_getParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize);
+</b><p> same as ZSTD_getCParams(), but @return a full `ZSTD_parameters` object instead of sub-component `ZSTD_compressionParameters`.
+ All fields of `ZSTD_frameParameters` are set to default : contentSize=1, checksum=0, noDictID=0
+</p></pre><BR>
+
+<pre><b>size_t ZSTD_checkCParams(ZSTD_compressionParameters params);
+</b><p> Ensure param values remain within authorized range
+</p></pre><BR>
+
+<pre><b>ZSTD_compressionParameters ZSTD_adjustCParams(ZSTD_compressionParameters cPar, unsigned long long srcSize, size_t dictSize);
+</b><p> optimize params for a given `srcSize` and `dictSize`.
+ both values are optional, select `0` if unknown.
+</p></pre><BR>
+
+<pre><b>size_t ZSTD_compress_advanced (ZSTD_CCtx* cctx,
+ void* dst, size_t dstCapacity,
+ const void* src, size_t srcSize,
+ const void* dict,size_t dictSize,
+ ZSTD_parameters params);
+</b><p> Same as ZSTD_compress_usingDict(), with fine-tune control over each compression parameter
+</p></pre><BR>
+
+<pre><b>size_t ZSTD_compress_usingCDict_advanced(ZSTD_CCtx* cctx,
+ void* dst, size_t dstCapacity,
+ const void* src, size_t srcSize,
+ const ZSTD_CDict* cdict, ZSTD_frameParameters fParams);
+</b><p> Same as ZSTD_compress_usingCDict(), with fine-tune control over frame parameters
+</p></pre><BR>
+
+<pre><b>size_t ZSTD_CCtx_loadDictionary_byReference(ZSTD_CCtx* cctx, const void* dict, size_t dictSize);
+</b><p> Same as ZSTD_CCtx_loadDictionary(), but dictionary content is referenced, instead of being copied into CCtx.
+ It saves some memory, but also requires that `dict` outlives its usage within `cctx`
+</p></pre><BR>
+
+<pre><b>size_t ZSTD_CCtx_loadDictionary_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictContentType_e dictContentType);
+</b><p> Same as ZSTD_CCtx_loadDictionary(), but gives finer control over
+ how to load the dictionary (by copy ? by reference ?)
+ and how to interpret it (automatic ? force raw mode ? full mode only ?)
+</p></pre><BR>
+
+<pre><b>size_t ZSTD_CCtx_refPrefix_advanced(ZSTD_CCtx* cctx, const void* prefix, size_t prefixSize, ZSTD_dictContentType_e dictContentType);
+</b><p> Same as ZSTD_CCtx_refPrefix(), but gives finer control over
+ and how to interpret prefix content (automatic ? force raw mode (default) ? full mode only ?)
</p></pre><BR>
<pre><b>ZSTD_CCtx_params* ZSTD_createCCtxParams(void);
</p></pre><BR>
+<a name="Chapter19"></a><h2>Advanced decompression functions</h2><pre></pre>
+
+<pre><b>unsigned ZSTD_isFrame(const void* buffer, size_t size);
+</b><p> Tells if the content of `buffer` starts with a valid Frame Identifier.
+ Note : Frame Identifier is 4 bytes. If `size < 4`, @return will always be 0.
+ Note 2 : Legacy Frame Identifiers are considered valid only if Legacy Support is enabled.
+ Note 3 : Skippable Frame Identifiers are considered valid.
+</p></pre><BR>
+
+<pre><b>ZSTD_DDict* ZSTD_createDDict_byReference(const void* dictBuffer, size_t dictSize);
+</b><p> Create a digested dictionary, ready to start decompression operation without startup delay.
+ Dictionary content is referenced, and therefore stays in dictBuffer.
+ It is important that dictBuffer outlives DDict,
+ it must remain read accessible throughout the lifetime of DDict
+</p></pre><BR>
+
+<pre><b>unsigned ZSTD_getDictID_fromDict(const void* dict, size_t dictSize);
+</b><p> Provides the dictID stored within dictionary.
+ if @return == 0, the dictionary is not conformant with Zstandard specification.
+ It can still be loaded, but as a content-only dictionary.
+</p></pre><BR>
+
+<pre><b>unsigned ZSTD_getDictID_fromDDict(const ZSTD_DDict* ddict);
+</b><p> Provides the dictID of the dictionary loaded into `ddict`.
+ If @return == 0, the dictionary is not conformant to Zstandard specification, or empty.
+ Non-conformant dictionaries can still be loaded, but as content-only dictionaries.
+</p></pre><BR>
+
+<pre><b>unsigned ZSTD_getDictID_fromFrame(const void* src, size_t srcSize);
+</b><p> Provides the dictID required to decompressed the frame stored within `src`.
+ If @return == 0, the dictID could not be decoded.
+ This could for one of the following reasons :
+ - The frame does not require a dictionary to be decoded (most common case).
+ - The frame was built with dictID intentionally removed. Whatever dictionary is necessary is a hidden information.
+ Note : this use case also happens when using a non-conformant dictionary.
+ - `srcSize` is too small, and as a result, the frame header could not be decoded (only possible if `srcSize < ZSTD_FRAMEHEADERSIZE_MAX`).
+ - This is not a Zstandard frame.
+ When identifying the exact failure cause, it's possible to use ZSTD_getFrameHeader(), which will provide a more precise error code.
+</p></pre><BR>
+
+<a name="Chapter20"></a><h2>Advanced streaming functions</h2><pre></pre>
+
+<h3>Advanced Streaming compression functions</h3><pre></pre><b><pre>size_t ZSTD_initCStream_srcSize(ZSTD_CStream* zcs, int compressionLevel, unsigned long long pledgedSrcSize); </b>/**< pledgedSrcSize must be correct. If it is not known at init time, use ZSTD_CONTENTSIZE_UNKNOWN. Note that, for compatibility with older programs, "0" also disables frame content size field. It may be enabled in the future. */<b>
+size_t ZSTD_initCStream_usingDict(ZSTD_CStream* zcs, const void* dict, size_t dictSize, int compressionLevel); </b>/**< creates of an internal CDict (incompatible with static CCtx), except if dict == NULL or dictSize < 8, in which case no dict is used. Note: dict is loaded with ZSTD_dm_auto (treated as a full zstd dictionary if it begins with ZSTD_MAGIC_DICTIONARY, else as raw content) and ZSTD_dlm_byCopy.*/<b>
+size_t ZSTD_initCStream_advanced(ZSTD_CStream* zcs, const void* dict, size_t dictSize,
+ ZSTD_parameters params, unsigned long long pledgedSrcSize); </b>/**< pledgedSrcSize must be correct. If srcSize is not known at init time, use value ZSTD_CONTENTSIZE_UNKNOWN. dict is loaded with ZSTD_dm_auto and ZSTD_dlm_byCopy. */<b>
+size_t ZSTD_initCStream_usingCDict(ZSTD_CStream* zcs, const ZSTD_CDict* cdict); </b>/**< note : cdict will just be referenced, and must outlive compression session */<b>
+size_t ZSTD_initCStream_usingCDict_advanced(ZSTD_CStream* zcs, const ZSTD_CDict* cdict, ZSTD_frameParameters fParams, unsigned long long pledgedSrcSize); </b>/**< same as ZSTD_initCStream_usingCDict(), with control over frame parameters. pledgedSrcSize must be correct. If srcSize is not known at init time, use value ZSTD_CONTENTSIZE_UNKNOWN. */<b>
+</pre></b><BR>
+<pre><b>size_t ZSTD_resetCStream(ZSTD_CStream* zcs, unsigned long long pledgedSrcSize);
+</b><p> start a new compression job, using same parameters from previous job.
+ This is typically useful to skip dictionary loading stage, since it will re-use it in-place.
+ Note that zcs must be init at least once before using ZSTD_resetCStream().
+ If pledgedSrcSize is not known at reset time, use macro ZSTD_CONTENTSIZE_UNKNOWN.
+ If pledgedSrcSize > 0, its value must be correct, as it will be written in header, and controlled at the end.
+ For the time being, pledgedSrcSize==0 is interpreted as "srcSize unknown" for compatibility with older programs,
+ but it will change to mean "empty" in future version, so use macro ZSTD_CONTENTSIZE_UNKNOWN instead.
+ @return : 0, or an error code (which can be tested using ZSTD_isError())
+
+</p></pre><BR>
+
+<pre><b>typedef struct {
+ unsigned long long ingested; </b>/* nb input bytes read and buffered */<b>
+ unsigned long long consumed; </b>/* nb input bytes actually compressed */<b>
+ unsigned long long produced; </b>/* nb of compressed bytes generated and buffered */<b>
+ unsigned long long flushed; </b>/* nb of compressed bytes flushed : not provided; can be tracked from caller side */<b>
+ unsigned currentJobID; </b>/* MT only : latest started job nb */<b>
+ unsigned nbActiveWorkers; </b>/* MT only : nb of workers actively compressing at probe time */<b>
+} ZSTD_frameProgression;
+</b></pre><BR>
+<pre><b>size_t ZSTD_toFlushNow(ZSTD_CCtx* cctx);
+</b><p> Tell how many bytes are ready to be flushed immediately.
+ Useful for multithreading scenarios (nbWorkers >= 1).
+ Probe the oldest active job, defined as oldest job not yet entirely flushed,
+ and check its output buffer.
+ @return : amount of data stored in oldest job and ready to be flushed immediately.
+ if @return == 0, it means either :
+ + there is no active job (could be checked with ZSTD_frameProgression()), or
+ + oldest job is still actively compressing data,
+ but everything it has produced has also been flushed so far,
+ therefore flush speed is limited by production speed of oldest job
+ irrespective of the speed of concurrent (and newer) jobs.
+
+</p></pre><BR>
+
+<h3>Advanced Streaming decompression functions</h3><pre></pre><b><pre>size_t ZSTD_initDStream_usingDict(ZSTD_DStream* zds, const void* dict, size_t dictSize); </b>/**< note: no dictionary will be used if dict == NULL or dictSize < 8 */<b>
+size_t ZSTD_initDStream_usingDDict(ZSTD_DStream* zds, const ZSTD_DDict* ddict); </b>/**< note : ddict is referenced, it must outlive decompression session */<b>
+size_t ZSTD_resetDStream(ZSTD_DStream* zds); </b>/**< re-use decompression parameters from previous init; saves dictionary loading */<b>
+</pre></b><BR>
+<a name="Chapter21"></a><h2>Buffer-less and synchronous inner streaming functions</h2><pre>
+ This is an advanced API, giving full control over buffer management, for users which need direct control over memory.
+ But it's also a complex one, with several restrictions, documented below.
+ Prefer normal streaming API for an easier experience.
+
+<BR></pre>
+
+<a name="Chapter22"></a><h2>Buffer-less streaming compression (synchronous mode)</h2><pre>
+ A ZSTD_CCtx object is required to track streaming operations.
+ Use ZSTD_createCCtx() / ZSTD_freeCCtx() to manage resource.
+ ZSTD_CCtx object can be re-used multiple times within successive compression operations.
+
+ Start by initializing a context.
+ Use ZSTD_compressBegin(), or ZSTD_compressBegin_usingDict() for dictionary compression,
+ or ZSTD_compressBegin_advanced(), for finer parameter control.
+ It's also possible to duplicate a reference context which has already been initialized, using ZSTD_copyCCtx()
+
+ Then, consume your input using ZSTD_compressContinue().
+ There are some important considerations to keep in mind when using this advanced function :
+ - ZSTD_compressContinue() has no internal buffer. It uses externally provided buffers only.
+ - Interface is synchronous : input is consumed entirely and produces 1+ compressed blocks.
+ - Caller must ensure there is enough space in `dst` to store compressed data under worst case scenario.
+ Worst case evaluation is provided by ZSTD_compressBound().
+ ZSTD_compressContinue() doesn't guarantee recover after a failed compression.
+ - ZSTD_compressContinue() presumes prior input ***is still accessible and unmodified*** (up to maximum distance size, see WindowLog).
+ It remembers all previous contiguous blocks, plus one separated memory segment (which can itself consists of multiple contiguous blocks)
+ - ZSTD_compressContinue() detects that prior input has been overwritten when `src` buffer overlaps.
+ In which case, it will "discard" the relevant memory section from its history.
+
+ Finish a frame with ZSTD_compressEnd(), which will write the last block(s) and optional checksum.
+ It's possible to use srcSize==0, in which case, it will write a final empty block to end the frame.
+ Without last block mark, frames are considered unfinished (hence corrupted) by compliant decoders.
+
+ `ZSTD_CCtx` object can be re-used (ZSTD_compressBegin()) to compress again.
+<BR></pre>
+
+<h3>Buffer-less streaming compression functions</h3><pre></pre><b><pre>size_t ZSTD_compressBegin(ZSTD_CCtx* cctx, int compressionLevel);
+size_t ZSTD_compressBegin_usingDict(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, int compressionLevel);
+size_t ZSTD_compressBegin_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_parameters params, unsigned long long pledgedSrcSize); </b>/**< pledgedSrcSize : If srcSize is not known at init time, use ZSTD_CONTENTSIZE_UNKNOWN */<b>
+size_t ZSTD_compressBegin_usingCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict); </b>/**< note: fails if cdict==NULL */<b>
+size_t ZSTD_compressBegin_usingCDict_advanced(ZSTD_CCtx* const cctx, const ZSTD_CDict* const cdict, ZSTD_frameParameters const fParams, unsigned long long const pledgedSrcSize); </b>/* compression parameters are already set within cdict. pledgedSrcSize must be correct. If srcSize is not known, use macro ZSTD_CONTENTSIZE_UNKNOWN */<b>
+size_t ZSTD_copyCCtx(ZSTD_CCtx* cctx, const ZSTD_CCtx* preparedCCtx, unsigned long long pledgedSrcSize); </b>/**< note: if pledgedSrcSize is not known, use ZSTD_CONTENTSIZE_UNKNOWN */<b>
+</pre></b><BR>
+<a name="Chapter23"></a><h2>Buffer-less streaming decompression (synchronous mode)</h2><pre>
+ A ZSTD_DCtx object is required to track streaming operations.
+ Use ZSTD_createDCtx() / ZSTD_freeDCtx() to manage it.
+ A ZSTD_DCtx object can be re-used multiple times.
+
+ First typical operation is to retrieve frame parameters, using ZSTD_getFrameHeader().
+ Frame header is extracted from the beginning of compressed frame, so providing only the frame's beginning is enough.
+ Data fragment must be large enough to ensure successful decoding.
+ `ZSTD_frameHeaderSize_max` bytes is guaranteed to always be large enough.
+ @result : 0 : successful decoding, the `ZSTD_frameHeader` structure is correctly filled.
+ >0 : `srcSize` is too small, please provide at least @result bytes on next attempt.
+ errorCode, which can be tested using ZSTD_isError().
+
+ It fills a ZSTD_frameHeader structure with important information to correctly decode the frame,
+ such as the dictionary ID, content size, or maximum back-reference distance (`windowSize`).
+ Note that these values could be wrong, either because of data corruption, or because a 3rd party deliberately spoofs false information.
+ As a consequence, check that values remain within valid application range.
+ For example, do not allocate memory blindly, check that `windowSize` is within expectation.
+ Each application can set its own limits, depending on local restrictions.
+ For extended interoperability, it is recommended to support `windowSize` of at least 8 MB.
+
+ ZSTD_decompressContinue() needs previous data blocks during decompression, up to `windowSize` bytes.
+ ZSTD_decompressContinue() is very sensitive to contiguity,
+ if 2 blocks don't follow each other, make sure that either the compressor breaks contiguity at the same place,
+ or that previous contiguous segment is large enough to properly handle maximum back-reference distance.
+ There are multiple ways to guarantee this condition.
+
+ The most memory efficient way is to use a round buffer of sufficient size.
+ Sufficient size is determined by invoking ZSTD_decodingBufferSize_min(),
+ which can @return an error code if required value is too large for current system (in 32-bits mode).
+ In a round buffer methodology, ZSTD_decompressContinue() decompresses each block next to previous one,
+ up to the moment there is not enough room left in the buffer to guarantee decoding another full block,
+ which maximum size is provided in `ZSTD_frameHeader` structure, field `blockSizeMax`.
+ At which point, decoding can resume from the beginning of the buffer.
+ Note that already decoded data stored in the buffer should be flushed before being overwritten.
+
+ There are alternatives possible, for example using two or more buffers of size `windowSize` each, though they consume more memory.
+
+ Finally, if you control the compression process, you can also ignore all buffer size rules,
+ as long as the encoder and decoder progress in "lock-step",
+ aka use exactly the same buffer sizes, break contiguity at the same place, etc.
+
+ Once buffers are setup, start decompression, with ZSTD_decompressBegin().
+ If decompression requires a dictionary, use ZSTD_decompressBegin_usingDict() or ZSTD_decompressBegin_usingDDict().
+
+ Then use ZSTD_nextSrcSizeToDecompress() and ZSTD_decompressContinue() alternatively.
+ ZSTD_nextSrcSizeToDecompress() tells how many bytes to provide as 'srcSize' to ZSTD_decompressContinue().
+ ZSTD_decompressContinue() requires this _exact_ amount of bytes, or it will fail.
+
+ @result of ZSTD_decompressContinue() is the number of bytes regenerated within 'dst' (necessarily <= dstCapacity).
+ It can be zero : it just means ZSTD_decompressContinue() has decoded some metadata item.
+ It can also be an error code, which can be tested with ZSTD_isError().
+
+ A frame is fully decoded when ZSTD_nextSrcSizeToDecompress() returns zero.
+ Context can then be reset to start a new decompression.
+
+ Note : it's possible to know if next input to present is a header or a block, using ZSTD_nextInputType().
+ This information is not required to properly decode a frame.
+
+ == Special case : skippable frames
+
+ Skippable frames allow integration of user-defined data into a flow of concatenated frames.
+ Skippable frames will be ignored (skipped) by decompressor.
+ The format of skippable frames is as follows :
+ a) Skippable frame ID - 4 Bytes, Little endian format, any value from 0x184D2A50 to 0x184D2A5F
+ b) Frame Size - 4 Bytes, Little endian format, unsigned 32-bits
+ c) Frame Content - any content (User Data) of length equal to Frame Size
+ For skippable frames ZSTD_getFrameHeader() returns zfhPtr->frameType==ZSTD_skippableFrame.
+ For skippable frames ZSTD_decompressContinue() always returns 0 : it only skips the content.
+<BR></pre>
+
+<h3>Buffer-less streaming decompression functions</h3><pre></pre><b><pre>typedef enum { ZSTD_frame, ZSTD_skippableFrame } ZSTD_frameType_e;
+typedef struct {
+ unsigned long long frameContentSize; </b>/* if == ZSTD_CONTENTSIZE_UNKNOWN, it means this field is not available. 0 means "empty" */<b>
+ unsigned long long windowSize; </b>/* can be very large, up to <= frameContentSize */<b>
+ unsigned blockSizeMax;
+ ZSTD_frameType_e frameType; </b>/* if == ZSTD_skippableFrame, frameContentSize is the size of skippable content */<b>
+ unsigned headerSize;
+ unsigned dictID;
+ unsigned checksumFlag;
+} ZSTD_frameHeader;
+</b>/** ZSTD_getFrameHeader() :<b>
+ * decode Frame Header, or requires larger `srcSize`.
+ * @return : 0, `zfhPtr` is correctly filled,
+ * >0, `srcSize` is too small, value is wanted `srcSize` amount,
+ * or an error code, which can be tested using ZSTD_isError() */
+size_t ZSTD_getFrameHeader(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize); </b>/**< doesn't consume input */<b>
+size_t ZSTD_decodingBufferSize_min(unsigned long long windowSize, unsigned long long frameContentSize); </b>/**< when frame content size is not known, pass in frameContentSize == ZSTD_CONTENTSIZE_UNKNOWN */<b>
+</pre></b><BR>
+<pre><b>typedef enum { ZSTDnit_frameHeader, ZSTDnit_blockHeader, ZSTDnit_block, ZSTDnit_lastBlock, ZSTDnit_checksum, ZSTDnit_skippableFrame } ZSTD_nextInputType_e;
+</b></pre><BR>
<h3>Advanced decompression API</h3><pre></pre><b><pre></b>/* ==================================== */<b>
</pre></b><BR>
<pre><b>size_t ZSTD_DCtx_loadDictionary(ZSTD_DCtx* dctx, const void* dict, size_t dictSize);
projects / thirdparty / zstd.git / commitdiff
